To address the material requirements for grouting reinforcement in fine sand strata, a novel silicate-modified polymer two-component grouting material was designed. In this material, the traditional organic polyol component of the two-component polymer was replaced with an inorganic silicate (water glass) component, along with the addition of tertiary amine catalysts, organotin catalysts, water. The response surface methodology (RSM) was used to statistically predict the performance of the modified polymer grouting material. The effects of four parameters (two-component mass ratio, tertiary amine catalyst content, organotin catalyst content, and water content) and their interactions on response variables (gelation time, polymer solids strength, cemented body strength) were investigated. Based on a comprehensive consideration of various performance requirements for grouting materials in loose fine sand strata, multi-objective optimization was employed to determine the optimal formulation of the modified polymer grouting material (A/B ratio of 0.85, tertiary amine catalyst at 2.48 %, organotin catalyst at 0.63 %, and water at 1.87 %). A series of experimental tests were conducted to evaluate the material properties of the optimal formulation, and its mechanical performance and microstructural characteristics were compared with those of traditional polymer grouting materials to verify the proposed formation mechanism of the modified polymer. The results demonstrated that the proposed design method effectively determines the optimal grouting material formulation. The optimized modified polymer grouting material exhibited excellent comprehensive performance. Finally, the optimized modified polymer grouting material was applied in a pavement repair project on a of a highway. After grouting, the structural layer's uniform integrity was significantly restored, the damaged areas were effectively repaired, the modified polymer slurry showed good diffusion, and the repair effect was satisfactory, meeting the engineering requirements for grouting in loose fine sand strata.

Groundwater is widely distributed in various rock and soil media and underground structures. Groundwater seepage inside the silty-fine sand layer causes infiltration erosion, leading to uneven settlement and cracking damage to the foundation and its structures. An analysis was conducted on the mechanisms of flowing soil and piping, and it was pointed out that flowing soil is caused by the effective gravity of sand particles, resulting in the floating and failure of sand particle groups due to the permeability greater than that of sand particles; Pipe surge refers to the migration and loss of movable fine particles, and the formation of water inflow channels through the interior of the silty-fine sand layer. Propose technical measures to improve the physical and mechanical properties of silty-fine sand layers and prevent infiltration damage through grouting. The mechanism of infiltration, splitting and compaction grouting was explained and analyzed, and the grouting materials such as plant glue modified cement sodium silicate, geopolymer, microbial solution, nano silica sol, emulsified asphalt, polyurethane, etc. were discussed and sorted out, aiming to contribute to improving the quality of silty-fine sand layer engineering projects.

The subgrade serves as the foundation of road construction, typically involving a significant amount of earthwork during its establishment. However, in coastal and desert areas, soil sources are often scarce. Local soil extraction significantly damages cultivated land, impacting the local ecological environment. Transporting soil over long distances inevitably raises construction costs. Fortunately, these regions often feature abundant fine sand distribution, presenting an opportunity to utilize it as subgrade filler in coastal regions. This review comprehensively introduces the properties of fine sand as a raw material, its engineering applications, and the associated construction technologies. It emphatically discusses the road use characteristics and treatment technology of fine sand filler and puts forward a prospect combining the characteristics and development trends of fine sand so as to provide a new perspective and basic material for the application of fine sand in the subgrade. To foster the adoption of fine sand in subgrade construction, it is recommended to advance research on the evaluation and treatment of fine sand foundations, analyze its suitability and structural behavior as a filler, and refine construction methodologies and quality control measures specific to fine sand subgrades.